1. Field of the Invention
This invention relates to a method of measuring the aberrations in a lens system.
2. Description of the Prior Art
The method as shown in FIG. 1 of the accompanying drawings is known as a method of measuring the aberrations in a lens system, namely, spherical aberration, coma, astigmatism and curvature of image field. In FIG. 1, which shows a prior art example for measuring spherical aberration, reference numeral 1 designates a point light source and reference numeral 2 denotes a collimater lens system for collimating the light from the light source 1. Designated by 3 is a so-called Hartmann's plate which serves to set the height of the light entering the entrance pupil of a lens 4 to be examined. Denoted by 5 are photosensitive surfaces which serve to record the light emergent from the lens. Spherical aberration is measured by the use of the light recorded with the photosensitive surface 5 placed forwardly of the imaging point of the lens and the light recorded with the photosensitive surface 5 placed rearwardly of that position by a finite distance d. That is, the conjugate exposure points on the two photosensitive surfaces have been linked together as shown in FIG. 2 of the accompanying drawings and light ray pursuit has been effected from a position at which the light rays cross the optical axis or the image plane, and the resultant data has been interpolated to thereby calculate a spherical aberration curve 6. This method, however, has required the two photosensitive surfaces provided at two locations to be accurately positioned and also has involved the necessity of highly accurately reading the position of each light ray and determining the light ray position. Moreover, two light ray positions must be read to determine a single light ray, and this has led to the disadvantage that much time is required for measurement and the result of the measurement becomes unstable.